Apparatus for determining ordnance parallax correctional factors



2 Sheets-Sheet 1 Filed Sept. 22,

INVENTOR 7fanniba2 OFOrR TTORNEYS w moo 3 umoum H/ m I I m 25 3 O Z :3III m '1 n; m 26m m3 3 s- RCH mom April 5, 1949. H. c. FORD APPARATUSFOR DETERMINING ORDNANCE PARALLAX CORRECTIONAL FACTORS Filed Sept. 22,1928 2 Sheets-Sheet 2 INVENTOR BY Hannibal QFo'Tfl d 5* 7 j! AZORNEYsPatented Apr. 5, 1949 APPARATUS FOR'DETERMINING ORDNANCE PARALLAXCORRECTIONAL FACTORS Hannibal C. Ford, Jamaica, N. Y., assignor to TheSperry Corporation, a corporation of Delaware Application September 22,1928, Serial No. 307,757 Renewed February 26, 1934 12 Claims. (Cl.23561.5)

This invention relates to apparatus for determining certain correctionalfactors involved in the firing of ordnance, more particularly ordnanceused against aerial targets.

The invention is particularly intended for use in systems in which gunsor the like are controlled from instruments known as directors whichtransmit to the guns indications of the train and elevation required forproperly aiming them. In the case of a gun located at an appreciabledistance from the director there is an angular difference between a linefrom the gun to the target and the line of sight from the director tothe target. In practice the gun will be aimed along a line differing inboth train and elevation from the line between it and the target toallow for the curvature of the trajectory of the projectiles and theeffect of other factors, such as their time of flight, wind, drift andthe like, all of which will be ignored as they do not enter into theparallax correction which depends solely upon the distance between thedirector and the gun, the angular relation between the target and theline joining the director and the gun and the range of the target.

It is accordingly necessary for accurate firing to apply to theindications of train transmitted from the director to the gun ahorizontal parallax correction, as it is usually called, to compensatefor the error due to the distance between the director and the gun in ahoridontal plane. If there be any appreciable distance between thedirector and the gun in a vertical plane it is also necessary to apply avertical parallax correction to the indications of gun elevationtransmitted from the director to the gun.

Both of these corrections have been applied, either singly or jointly asrequired, in systems for controlling the firing of ordnance usedagainst.

surface targets. In the case of aerial targets, however, a furthervertical parallax correction is required due to the horizontal distancebetween the director and the gun as the line representing this distancedoes not lie in the same plane in which the line from the gun to thetarget lies, as is the case with surface targets.

It is accordingly an object of this invention to provide apparatus fordetermining the correction required for the accurate aiming of a gun inelevation from a director by calculating the vertical parallax due tothe vertical distance between the director and the gun and the verticalparallax due to the horizontal distance between the director and the gunand correcting the gun elevation in accordance with these two quantitiesto give the required elevation for accurate pointing of the gun againstan aerial target insofar as parallax errors are concerned.

It is a further object of the invention to pro- V vide in connectionwith both horizontal and vertical parallax corrections and for bothsurface and aerial targets an apparatus for determining such correctionsby computing the values of the parallax corrections due to unit baselength and converting these values to the required values by multiplyingthem by the ratio of the actual base length to the unit base length.

One form of apparatus which may be employed for these purposes consistsof an instrument for computing the parallax correction due to a unithorizontal base length and converting this value into the requiredcorrection by multiplying it by the ratio of the actual horizontal baselength to the unit horizontal base length and transmitting to the gunthe indications of train corrected in accordance with the requiredparallax correction.

The invention further comprises mechanism in the instrument forcomputing the vertical parallax corrections due to both horizontal andvertical unit base lengths and converting these values into the requiredvertical parallax corrections by multiplying them by the ratios of theactual horizontal and vertical base lengths to the unit horizontal andvertical base lengths. The instrument also combines the verticalparallax corections due to a horizontal base and to a vertical base andcorrects the indications of gun elevation transmitted from the directorin ac cordance with such parallax correction in order that the gun maybe accurately pointed.

The particular nature of the invention as well as other objects andadvantages thereof will appear most clearly from a description of apreferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a diagram used in deriving the equations solved by theapparatus of the invention;

Fig. 2 is a simplified diagram of one form of apparatus in which theinvention may be embodied;

Fig. 3 is an enlarged perspective view of the yielding driving mechanismof Fig. 2; and

Fig. 4 is a diagram similar to and showing parts of some of the elementsof Fig. 2 but with a different form of operating mechanism.

Referring to Fig. 1, the point D represents an observing station ordirector located at a unit distance Uv above the plane of reference,usually a horizontal plane, in which a gun is located at the point Glying at a unit distance UH from a point A directly below the directorD. The point T represents an aerial target, the range R of which fromthe director is therefore represented by the line DT. C represents apoint in the reference plane below the target, the line TC beingperpendicular to the plane and parallel to the line DA. The line ACrepresents the direction of the point C from the director so that theexternal angle GAC measured in a clockwise direction represents thebearing of the point C from A referred to the base line UH, this anglebeing designated B for convenience in future reference.

The line GJ represents a line from the point G perpendicular to the lineAC and its length is represented by UH sin B. The portion of the line ACbetween A and J is represented by UH cosine B.

JK is a line from the point J to the line AT perpendicular to the latterand since in practice the portion K--T of this line is relatively greatcompared with the portion AK and differs but slightly from the distanceD-T or R, the portion K--T may be assumed to be equal to R.

The line DM is a line parallel to the line AC at a distance Uv from thelatter. The angle TDM, therefore, represents the elevation of the lineof sight from the director D to the target measured relative to the lineDM which is parallel to the reference plane. For convenience this angleTDM will be designated Ev. Since the range of the target is relativelygreat as compared with the distance Uv the angle TAC may be regarded asapproximately equal to Ev.

The length of the line JK is accordingly represented by UH cos B sin Ev.The angle JTK is, therefore, approximately U cos B sin E R whichrepresents the vertical parallax due to the unit base UH. Forconvenience this unit parallax factor will be designated VPUH.

DN is a line from the point D perpendicular to the line AT. The angleDAN is therefore equal to 90Ev so that the length of the line DN is Uvsin (90-Ev) or Uv cos Ev. The angle DTA is therefore approximately U cosE which represents the vertical parallax due to the unit base Uv and forconvenience this unit parallax factor will be designated VPUV. The totalunit parallax correction in a plane perpendicular to the referenceplane, this correction being in the vertical plane when the referenceplane is horizontal, will be designated VPUHV and is equal to VPUH -VPUThe angle CGT represents the actual elevation of the line from the gunto the target with respect to the reference plane, or in other words,the elevation which must actually be given to the gun to allow forvertical arallax, all other factors being neglected. That is, this angleis equal to the algebraic sum of the angle Ev and the total parallaxcorrection angle VPUHV.

Since the portion of the line AC lying between J and C is relativelygreat in practice as compared with the portion lying between A and J, itmay be assumed equal to R cos Ev without appreciable error. Since theline GJ is represented by UH sin 3 the angle GCJ is approximately equalto U sin'B R cos E this angle being the unit parallax correction in theplane of reference due to the unit base UH and for convenience it willbe designated HPUH.

The angle FGC represents the actual bearing of the line from the gun tothe target with respect to the base line UH, or in other words, thebearing which must actually be given to the gun to allow for horizontalparallax. That is, this angle is equal to the algebraic sum of the angleB and the parallax correction angle HPUH.

In Fig. 2 there is shown in diagrammatic form an instrument forcalculating the quantities derived from Fig. 1. It will be understoodthat all the parts while shown diagrammatically are in practice mountedupon a member I rotatably mounted upon a pedestal 2 within an annularrack 3 fixed to the top of the pedestal. Meshing with the rack 3 is apinion 4 on a shaft 5 suitably mounted upon the member I and carrying agear 6 meshing with a pinion 1 on the lower end of a shaft 8, the upperend of which carries a bevel gear '9 meshing with a corresponding gearID on the end of a shaft ll. Meshing with the gear I0 is a bevel gear l2on the lower end of a shaft l3 which is connected by a pair of bevelgears l4 with a shaft 15 which is connected by bevel gears l6, shaft I1and bevel gears l8 to a pair of hand wheels l9 adapted to be operated bythe trainer of the instrument to follow the movement of a target asviewed by him through a telescope 20 suitably mounted to turn in trainwith the member l and in elevation about an axis represented by a shaft2| parallel to the member I. A dial 22 reading against a fixed index 23to give indications of train or bearing B of the target with respect tothe base line UH of Fig.1, is mounted at the end of a shaft 24 that isdriven from the shaft l5 by a pair of gears 25.

The telescope 20 is moved in elevation by means of a gear 26 on theshaft 2| and meshing with a worm 21 connected by a pair of bevel gears28 to a shaft 29 which by a pair of bevel gears 30 is connected to aworm 3| meshing with a gear 32 on the shaft 33 of a pointers telescope34 which is suitably mounted to move in train with the telescope 20. Theshaft 29 extends beyond the bevel gears 30 and is connected by bevelgears 35, shaft 36, and bevel gears 31 to a pair of hand wheels 38adapted to be operated by the pointer of the instrument who follows themove ,ment of the target in elevation. The elevation angle Ev isindicated :by a dial 39 reading against a fixed index 40 and attached tothe end of a shaft 4| which is connected by bevel gears 42 to theelevation shaft 29.

Shaft H which is rotated in accordance with the bearing angle B by thetrainer is connected through bevel gears 43 to a shaft 44 carrying atone end a pinion 45 which meshes with a gear 46 meshing in turn withgear 41 which will, therefore, be turned in accordance with the angle B.Gear 41 is provided with a radial slot 48 within which is mounted aslidable block 49 carrying a rod 50, which extends through a spiralgroove 5i in a gear 52 which is rotated in accordance with values ofrange as will now be described, the spiral groove being arranged tocause a radial movement of the rod 50 in accordance with reciprocalvalues of range, that is, in accordance with A crank 53 on the end of a,shaft 54 is adapted to be turned in accordance with values of range RSEARCH as received from a suitable instrument, such as a range finder.The values are indicated by a dial 55 reading against a fixed index 56and mounted upon the end of a shaft 51 connected by bevel gears 58 tothe shaft 54. The shaft 54 is also connected by bevel gears 59 to ashaft 60 having its other end connected to the center 6| of adifferential 6|. One side 6|" of the differential carries a gear 62meshing with the gear 46, so that this side of the differential receivesa movement proportional to the bearing angle B as does the gear 41. Thesecond side 6I' of the differential carries a gear 63 meshing with thegear 52. By virtue of the differential 6| the gears 41 and 52 are turnedin accordance with the bearing angle B and the gear 52 receives adisplacement relatively to the gear 41 in accordance with range R sothat the rod 50 is positioned in accordance with bearing B andreciprocals of range The rod 50 also passes through a slotted arm of arectangular slide 54 which, therefore, receives a movement proportionalto U cos B R it being understood that the quantity Us which is aconstant representing a unit length of base line is provided for bysuitable proportioning of the parts. The rod 50 also passes through aslotted arm of a second rectangular slide 65 which receives a movementproportional to U sin B R The rod I2 is attached to a block I3 slidablymounted in a radial slot I4 in a gear 15 adapted to be rotated inaccordance with values of the elevation angle Ev by the followingelements. Meshing with the gear 15 is a pinion I6 on the end of a shaft11 which is connected through bevel gears 18, shaft I9 and bevel gears80 to the Ev shaft 29. The shaft I1 also carries a gear 8| meshing witha gear 82 attached to the second side 68" of the differential 68. Byvirtue of the differential, the gears 10' and I5 are moved in accordancewith values of the angle Ev and the gear I is displaced relatively tothe gear I in accordance with values of so that the rod I2 is positionedin accordance with both of these quantities. The rod 12 also extendsthrough a slotted arm of a rectangular slide 83 which is moved inaccordance with the quantity Uv cos E R The quantity Uv, which is aconstant represent ing a unit length of base line is provided for in theinstrument by suitable proportioning of its parts.

As shown most clearly in Fig. 3 the vertical arm of the slide 65 isprovided with a rack meshing with a pinion 84 loose on a shaft 85 andhaving a pin 86 normally held against a pin 81 projecting from the shaftby a spring 88 attached at one end of the pinion 84 and at the other endto a collar 89 fastened to the shaft 85. A similar but reversely woundspring 90 is attached at one end to the collar 89 and at the other endto a pinion 9| also loosely mounted on the shaft 85 similarly to pinion84. The pinion 9I carries a pin 92 normally held by the action of thespring 90 in engagement with a pin 93 attached to the shaft. The pinion9| meshes with the larger gear of a compound gear 94, the smaller gearof which meshes with a rack on the vertical arm of a rectangular slide95. The mechanism described in this paragraph constitutes a yieldingdriving connection between the slide 65 and the slide 95, the operationand purpose of which will be hereinafter explained.

Slidably mounted on the horizontal arm of the slide 95 is a carriage 96provided with a rod 91 extending through a slot in this arm and into aslotted link 98 restrained at one end by a fixed rod 99 passing throughthe slot. The other end of the link is attached to a reciprocating rackI00 meshing with a pinion IOI on a shaft I02 connected through bevelgears I 03 to a shaft I04 having detachably secured to its lower end agear I05 meshing with a gear I06 detachably secured to the upper end ofa shaft I01.

It has been previously stated that the instrument computes the value ofthe horizontal parallax correction for a unit horizontal base length andconverts this correction into the required correction by multiplying itby the ratio of the actual horizontal base length to the unit horizontalbase length. Since for any particular installation the actual baselength is fixed, the gears I05 and I06 perform the converting operation,their ratio being suitably selected in accordance with the ratio betweenactual and unit base lengths. By being detachably secured to theirshafts they may be readily changed to adapt them to differentinstallations with different ratios.

The shaft I0! is connected through bevel gears I08 to the side I09 of adifferential I09, the center I09 of which is attached to a shaft IIOconnected by bevel gears II I to a shaft II2 for actuating a transmitterI I3 of any suitable type for sending training indications to thecontrolled gun. The shaft II 2 drives through bevel gears II4, shaft 5and bevel gears II6, a dial II'I reading against a fixed index I I9 toshow the values of the indications transmitted to the gun, so that ifthe transmission system fails indications can be obtained and sent tothe gun by other means.

The other side I09 of the differential I09 carries a pinion ||9 meshingwith a gear I20 on the other end of the shaft 44 which as previouslyexplained receives a movement proportional to the bearing angle B fromthe trainer's hand wheel I9.

The shaft 29 is connected through bevel gears I2I, shaft I22 and bevelgears I23 to the side I24" of a differential I24. This side also carriesa pinion I25 meshing with a gear sector I26, which thus receives fromthe shaft 29 an angular movement proportional to the elevation angle Ev.The gear sector carries a rod |2I extending rearwardly into a slottedarm of an inverted U-shaped slide I28 which receives a movementproportional to cos Ev from the gear sector I26. The other slotted armof the slide receives the forwardly extending portion of the rod 91.Since as previously described the slide 65 receives a movementproportional to U Sill B R the slide 95 receives through the yieldingdriving connection consisting of the elements designated 84 to 90, bothinclusive, a corresponding movement.

Under normal conditions of operation the spring 88 holds the pins 86 and81 in engagement so that the movement imparted to the gear 84 by theslide 05 is transmitted through the shaft 85 and the pins 93 and 92which are held in engagement by the spring 90 as if the shaft con.-stituted a rigid connection between the pinions. Under usual conditionsand for consistent values of the movements of the slide 95 representingand slide I28 representing cos Ev, the relation of the slides, pin 91and link 98 will be such as to cause a movement of rack I with nopossibility of disengagement of the rack from pinion IOI. In practicestops will be provided for limiting the movement of the rack to preventsuch disengagement, but when this is done there is a possibility whenthe instrument is operated for unusual and inconsistent values of thequantities UH Sill B R and cos Ev that the rack I00 will reach one 01'the other of its stops before the slides have reached positionscorresponding to those required by the conditions under which theinstru-.

ment is being operated.

When this occurs the movement of slide 95 is prevented through the pin9! and link 98 connected to the rack I00, the movement of which has beenstopped. The slide 65 may however continue to move because one or theother of the springs 88 or 89 will be placed under increased tension topermit separation of the pins 86 and 81 or 92 and 93 according to thedirection in which the gear 84 is being turned by the slide 65 aftermovement of the gear 9I has been prevented by the stopping of slide 95which is connected to the gear by the compound gear 94. The springs 88and 90 are so designed that while under normal conditions of operationthey hold the pins 86 and 81 on the one hand and the pins 92 and 93 onthe other hand in engagement, they will yield and permit separation ofthe pins before there is any danger of damage to any of the elements ofthe instrument by continued movement of slide 65 after the rack I00 hasreached its limits of movement.

As previously explained the slide 95 receives a movement proportional toU sin B R and the slide I28 receives a movement proportional to cos Ev.These slides are so related as to displace through the rod 91 and link98 the rack I00 in accordance with the quantity UH sin B R cos E 8 Thismovement is transmitted to the pinion IOI, shaft I02, bevel gears I03and shaft I04, to the gear I05 which in conjunction with the gear I06multiplies this quantity by the ratio of the actual base length Ln tothe unit base length UH to give the quantity LH UH Sill B U R cos E L;sin B R cos E which is the horizontal parallax correction HPn due to theactual horizontal base length Ln. This quantity is reproduced in themovement of the side I09 of the differential I09 throughthe shaft I0!and bevel gears I08. Since, as previously explained, the other side I09" receives a movement proportional to the bearing angle B from thetrainers hand wheels, the center I 09 receives a movement proportionalto the algebraic sum of the bearing angle and the horizontal parallaxcorrection, that is, BiHPL The resultant movement of the centre of thedifferential causes through shaft IIO, bevel gears III and shaft IIZ acorresponding actuation of the transmitter I I3 to send to the gunindications of the required train corrected for horizontal parallax. Atthe same time the measure of this quantity is carried from shaft II2, bybevel gears II I, shaft H5 and bevel gears II6 to the dial II! where theindication of the quantity is read against its index II 8.

It has previously been explained that the slide 83 is moved inaccordance with the quantity The horizontal arm of this slide isprovided with a rack which meshes with a pinion I 29 on a shaft I30connected through bevel gears I3I, shaft I32 and bevel gears I33 to ashaft I34 having detachably secured to its upper end a gear I35 meshingwith a gear I36 detachably secured to the lower end of a shaft I31.These gears perform the function of converting the quantity whichrepresents the vertical parallax due to the unit base Uv into thevertical parallax due to the actual base Lv, their ratio beingproportional In other Words, they multiply the quantity U cos E R by theratio Lv UV giving L cos E R blliliibil EiUUit't extends forwardly intothe slotted arm of a U-shaped slide I4I the other slotted arm of whichreceives the rear end of a rod I42 projecting from a carriage I43slidably mounted on the vertical arm of a rectangular slide I44, the armbeing slotted to permit the passage through it of the rod. Thehorizontal arm of this slide is provided with a rack meshing with apinion I45 on a shaft I46 to which is detachably secured a gear I41meshing with a gear I48 detachably secured to the side I40" of thedifferential I40. As previously explained slide 64 receives a movementproportional to U cos B R U cos B sin E ,which is the vertical parallaxcorrection VPu due to the unit horizontal base line UH. The gears I41and I48 have a ratio proportional to UH the same as the gears I and I06and they multiply the quantity U cos B sin E is. UH giving LH cos B sinE; R

which is the vertical parallax correction VlF'r. due the actualhorizontal base Ln.

Since the centre I40' of the differential I40 receives a movementproportional to the vertical parallax correction due to the actualvertical base Lv and the side I40" receives a movement proportional tothe vertical parallax correction due to the actual horizontal base Ln,the other side I40 receives a movement proportional to the algebraic sumof these corrections, that is, VPn iVPr. or VPLHV the total verticalparallax correction. This side is rigidly connected to the side I24' ofdifferential I24 of which the center I24 is connected to a shaft I5I,which thus receives a movement proportional to the elevation angle Evthrough the side I24" and the total vertical parallax correction VPLHVthrough side I24 of the differential, the movement of the shaft thusrepresenting the elevation indication which should be transmitted to thegun as corrected for vertical parallax, or nvivm This is accomplished bya drive from the shaft I 5I through bevel gears I52, shaft I53, bevelgears I54, shaft I55, bevel gears I56, shaft I51, bevel gears I58 andshaft I59 of a transmitter I60 connected to a suitable receiver at thegun. The shaft I55 also drives through bevel gears I6I and shaft I62, adial I63 reading against a fixed index I64 to give indications of thecorrected elevation being transmitted to the guns for use in case thetransmission system fails and it is necessary to convey the informationby other means.

In Fig. 4 is shown a modified form of operating connection between theslides 65 and 95 and the rack I00. In this arrangement, the slide 65 ofFig. 2 drives through pinion 84, shaft I66, and pinion I61 a pinion I68on the side I69 of a diiferential I69. The other side I69 of thedifferential carries a pinion I10 meshing with a pinion I1I on a shaftI12 which is connected through a pair of pinions I13, shaft I14 andpinion I15 with a gear I16 having integral therewith the compound gearand pinion 94 meshing with the rack of the slide 95.

The center I69 of the differential is attached to a shaft I18 whichcarries a cam I19 having substantially semi-circular portions of unequalradii. The cam operates a contact device I of the general type shown inmore detail in my Patent No. 1,577,618, granted March 23, 1926, forSpeed regulating mechanism. In the normal condition of the device, itsroller I8I engages an intermediate cam portion between the dwells of thecam I19 and the contact arm I82 of the device lies midway between fixedcontacts I83 and I84. The contact arm has a portion insulated from therest of the device and electrically connected by a conductor I85 to thepositive main I86 of a source of supply. The contacts I83 and I84 areconnected by a conductors I81 and I88 respectively to the reverselywound field windings of a motor I89 of any suitable type and the circuitis completed through its armature and then by a conductor I90 leading tothe negative main I9I. The motor drives through shaft I92 and pinion IOIthe rack I00 corresponding to the similarly designated rack of Fig. 2.The shaft I92 also drives through bevel gears I94 shaft I04 of Fig. 2.

In the operation of this modification of the invention the movement ofslide 65 is transmitted through pinion 84, shaft I66 and pinions I61 andI68 to the side I69" of difierential I69. Regarding its other side I69as fixed since it is connected to the slide 95, the center I69 will beturned to turn the cam I19 by shaft I18. This will actuate the contactdevice I80 to shift its arm I 8-2 into engagement with one or the otherof the contacts I83 or I84 according to whether the roller I8I movesoutwardly or inwardly as a result of the turning of the cam. A circuitis, therefore, established from the main I86 through conductor I85, armI82, one or the other of the contacts I83 or I84 and the conductor I81or I88 connected thereto, the corresponding field winding of the motorI89, the armature of the motor and conductor I90 leading to the othermain I9I. Through shaft I92 and pinion IOI the motor moves the rack I00to position the link 98 and rod 91 that are shown in Fig. 2. Themovement imparted to the rod displaces the slide 95 and through thecompounded pinion and gear 94, pinion I15, shaft I14, pinions I13, shaftI12, pinions HI and I10, the side I69 of the diiferential will bedisplaced. Regarding the other side I69" as now fixed, the center I69will be displaced, but in the opposite direction to its formerdisplacement to oppositely turn the cam I19 to restore the contactdevice I80 to its normal position and open the circuit of the motor I89.

The elements above described constitute a follow-up system by which themovement of slide 65 is reproduced at slide 95 and the correspondingmovement of the rack I is also produced, as in the case of these sameelements described in connection with Fig. 2. If under unusual andinconsistent values of the quantities involved the rack I00 reaches oneof its stops before the slide 65 reaches its required position the motorwill be stopped, but the cam I19 will continue to turn without offeringany appreciable resistance to the movement of the slide 65, so thatthere is no danger of damage to any of the elements of the instrument.In other words, the modification shown in Fig. 4 performs the functionof the yielding driving connection of Figs. 2 and 3 but has theadvantage over such a mechanical drive in that additional power from themotor is obtained for operating the elements of the instrument. When theslide 65 again reaches a position corresponding to consistent values ofthe quantities involved the motor will again become effective to actuatethe rack Hill as above described.

While the invention has been described in connection with an aerialtarget it is equally adapted for controlling ordnance used againstsurface targets. In this case the angle Ev is zero and there is novertical parallax due to the base UH, but only that due to the base Uvand the horizontal parallax due to the base UH. In other words, theexpression U cos B sin E R representing the vertical parallax due to thebase UH becomes zero. In other respects the invention is the same andthe instrument operates as described in connection with an aerialtarget.

While certain preferred embodiments of the invention have beendescribed, it will be understood that it may be embodied in other formsand that various changes in structural details may be made withoutdeparting from the principle of the invention as defined in the appendedclaims.

I claim:

1. In an instrument for determining an angular correctional factordepending on a, plurality of variables, the combination of means forcomputing the value of the factor for unit value of one of the variablesand means for multiplying the value of the factor by the ratio betweenthe actual value of the variable and the unit value thereof said secondmentioned means being detachably associated with said first mentionedmeans to allow for altering of the multiplying ratio when the ratiobetween the actual value of the variable and unit value thereof isaltered.

2. In an instrument for determining a parallax correction thecombination of means for computing the value of the correction for aunit base length and means for multiplying the value of the correctionby the ratio between the actual base length and the unit base length,said multiplying means being detachably associated with said com-.puting means to provide for altering the multiplying ratio to conformwith the ratio between the actual base length and unit base length.

lar relation of an object with respect to'a base line lying in areference plane and between two separated points from one of which theangular relation is known, the combination of means for determining theangular relation corresponding to a unit length of the base line betweenthe points including an element displaceable in accordance with afunction of the known angular relation of the object, a secondelementdisplaceable in accordance with a function of the distance of the objectfrom the point from which the angular relation is known, means forcombining the displacements of the members, a third element displaceablein accordance with a function of the angular relation of the object withrespect to the reference plane, and means for combining the movements ofthe first combining means and the third element, means for multiplyingthe movement of the second combining means by the ratio of the actuallength of the line between the points to a unit length of said line andmeans for correcting the known angular relation of the object inaccordance with the correctional alteration of the angular relation asdetermined by the last named means.

5. In an instrument for determining a parallax correction, thecombination of means for determining the parallax correction due to aunit length of the base line between two points including an elementdisplaceable in accordance with a function of the bearing of a distantobject from one of the points, a second element displaceable inaccordance with a function of the range of the object, means forcombining the displacements of the members, a third element displaceablein accordance with a function of the angle of elevation of the objectand means for combining the movements of the first combining means andthe third element and means for multiplying the movement of the secondcombining means by the ratio between the actual length of the base lineand the unit length thereof.

6. In an instrument for determining a parallax correction, thecombination of means for determining the parallax correction due to aunit length of the base line between two points including an elementdisplaceable in accordance with a function of the elevation of a distantobject, a second element displaceable in accordance with a function ofthe range of the object and means for combining these displacements ofthe members, and means for multiplying the movement of the combiningmeans by the ratio between the actual length of the base line and theunit length thereof.

'7. In an instrument for determining the hearing of an object from oneof two separated points from the other of which the bearing is known,the combination of means for determining the parallax corrections due toa unit length of the base line between the points including an elementdisplaceable in accordance with a function of the bearing of the object,a second element displaceable in accordance with a function of the rangeof the object, means for combining the displacements of the members, athird element displaceable in accordance with a function of the angle ofelevation of the object and means for combining the movements of thefirst combining means and the third element, means for multiplying themovement of the second combining meansby the ratio between th actuallength of the base line and the unit length ther of and means forcorrecting the bearing of the object from one of the points by thedetermined SEARCH R9959 parallax correction for the actual base lengthto give the bearing of the object from the other point.

8. In an instrument for deter-mining a parallax correction, thecombination of means for determining the parallax correction due to aunit length of the base line between two points including an elementdisplaceable in accordance with a function of the elevation of a distantobject, a second element displaceable in accordance with a function ofthe range of the object and means for combining the displacements of themembers, and means for multiplying the movement of the combining meansby the ratio between the actual length of the base line, and the unitbase length, means for determining a second parallax correction due to aunit length of a second base line between one of said two points and athird point including an element displaceable in accordance with afunction of the bearing of the object, a second element displaceable inaccordance with the range of the object, means for combining thedisplacements of the members, a part displaceable in accordance with afunction of the angle of elevation of the object and means for combiningthe movements of the second combining means and the part, means formultiplying the movement of the third combining means by the ratiobetween the actual length of the second base line and the unit lengththereof, and means for combining the movements of the two means fordetermining parallax corrections to give the total parallax corrections.

9. In an instrument for determining the angular relation of an objectwith respect to a base line lying in a reference plane and between twoseparated points from one of which the angular relation is known, thecombination of means for determining the angular relation correspondingto a unit length of the base line between the points including anelement displaceable in accordance with a function of the known angularrelation of the object, a second element displaceable in accordance witha function of the distance of the object from the point from which theangular relation is known, means for combining the displacements of themembers, a third element adapted to be displaced in accordance with thecombined displacements of the elements, a yielding driving connectionbetween the combining means and the third element, a fourth elementdisplaceable in accordance with a func-- tion of the angular relation ofthe object with respect to the reference plane, and means for combiningthe movements of the third and fourth elements, means for multiplyingthe movement of the second combining means by the ratio of the actuallength of the base line between the points to the unit length of saidline and means for correcting the known angular relation of the objectin accordance with the correctional alteration of the angular relationas determined by the last named means.

10. In apparatus for transmitting the movement of one member to anothermember, the combination of an element operatively connected to the firstmember, a part movably related to the element, means connected betweenthe element and the part for normally holding them in fixed relation butadapted to yield to permit relative movement between them, a secondelement operatively connected to the second member and movably relatedto the part and means connected between th second element and the partfor normally holding them in fixed relation but adapted to yield topermit relative movement between them.

11. In apparatus for transmitting the movements of one member to anothermember, the combination of a gear operatively connected to the firstmember, a shaft upon which the gear is movably mounted, resilient meansconnected between the gear and the shaft for normally holding them infixed relation but adapted to yield to permit relative movement betweenthem, a second gear operatively connected to th second member andmovably mounted upon the shaft and resilient means connected between thesecond gear and the shaft for normally holding them in fixed relationbut adapted to yield to permit relative movement between them.

12. In an instrument for determining training and elevational movementsfor a gun used against an aerial target including horizontal andvertical parallax corrections, the combination of means operable inaccordance with required uncorrected movements of the gun in elevationand train, means for computing vertical parallax corrections due tovertical and horizontal unit bases, means for computing a horizontalparallax correction due to the horizontal unit base, mechanisms formultiplying the respective computed corrections by the ratios betweenthe unit bases and the actual vertical and horizontal bases, and meansfor combining the vertical and horizontal parallax corrections with therequired elevational and training movements effected by the first namedmeans.

HAN'NIBAL C. FORD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 714,786 Day Dec. 2, 1902 934,223Scott Sept. 14, 1909 996,331 Hall June 27, 1911 1,135,596 Locarni Apr.13, 1915 1,232,968 Pollen et a1 July 10, 1917 1,370,204 Ford Mar. 1,1921 1,392,959 Meitner Oct. 11, 1921 1,419,283 Mattson June 13, 19221,438,832 Kaminski Dec. 12, 1922 1,453,104 Gray Apr. 24, 1923 1,487,460Hansson Mar. 18, 1924 1,492,899 Schneider May 6, 1924 1,512,103 KaminskiOct. 21, 1924 1,532,754 Kaminski Apr. 7, 1925 1,615,509 Grotendorst Jan.25, 1927 1,684,315 Haller Sept. 11, 1928

